How it works

The PC sends display data over the parallel port and controls the LCD’s Enable and Register Select lines. External 10 kΩ pull-ups support the control interface, while the potentiometer sets LCD contrast.

This design targets a traditional hardware printer port and software written in Borland C++. A typical USB printer adapter does not expose the same register-level interface and is not a direct replacement.

Original schematic

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Figure 1 · NewCircuits archive · Download image ↓

On the bench

Confirm the LCD pinout, logic voltage, and port wiring before connection. The preserved source ZIP is historical software and may need modification for a modern operating system.

Resources & provenance

Rewritten from the original circuits/pcr/s40mn76_pcr001.php page. Component values and historical performance claims have not been independently bench-tested. The circuit figures have had their watermarks removed.

↓   sw_pcr001.zipOriginal ZIP · 886 bytesBrowse all surviving downloads →